Variable density and variable persistent organic memory devices, methods, and fabrication

ABSTRACT

An organic memory device comprising two electrodes having a selectively conductive decay media between the two electrodes provides a capability to control a persistence level for information stored in an organic memory cell. A resistive state of the cell controls a conductive decay rate of the cell. A high and/or low resistive state can provide a fast and/or slow rate of conductive decay. One aspect of the present invention can have a high resistive state equating to an exponential conductive decay rate. Another aspect of the present invention can have a low resistive state equating to a logarithmic conductive decay rate. Yet another aspect relates to control of an organic memory device by determining a power state and setting a resistive state of an organic memory cell based upon a current power state and/or an imminent power state.

TECHNICAL FIELD

The present invention relates generally to organic memory devices and,in particular, to organic memory devices with variable persistent memorystorage capabilities.

BACKGROUND ART

The volume, use and complexity of computers and electronic devices arecontinually increasing. Computers consistently become more powerfulwhile new and improved electronic devices are continually developed(e.g., digital audio players, video players). Additionally, the growthand use of digital media (e.g., digital audio, video, images, and thelike) have further pushed development of these devices. Such growth anddevelopment has vastly increased the amount of informationdesired/required to be stored and maintained for computer and electronicdevices.

Generally, information is stored and maintained in one or more of anumber of types of storage devices. Storage devices include long termstorage mediums such as, for example, hard disk drives, compact diskdrives and corresponding media, digital video disk (DVD) drives, and thelike. The long term storage mediums typically store larger amounts ofinformation at a lower cost, but are slower than other types of storagedevices. Storage devices also include memory devices which are often,but not always, short term storage mediums. Memory devices tend to besubstantially faster than long term storage mediums. Such memory devicesinclude, for example, dynamic random access memory (DRAM), static randomaccess memory (SRAM), double data rate memory (DDR), flash memory, readonly memory (ROM), and the like. Memory devices are subdivided intovolatile and non-volatile types. Volatile memory devices generally losetheir information if they lose power and typically require periodicrefresh cycles to maintain their information. Volatile memory devicesinclude, for example, random access memory (RAM), DRAM, SRAM and thelike. Non-volatile memory devices maintain their information whether ornot power is maintained to the devices. Non-volatile memory devicesinclude, but are not limited to, ROM, programmable read only memory(PROM), erasable programmable read only memory (EPROM), flash memory andthe like. Volatile memory devices generally provide faster operation ata lower cost as compared to non-volatile memory devices.

Memory devices generally include arrays of memory cells. Each memorycell can be accessed or “read”, “written”, and “erased” withinformation. The memory cells maintain information in an “OFF” or an“ON” state (e.g., are limited to 2 states), also referred to as “0” and“1”. Typically, a memory device is addressed to retrieve a specifiednumber of byte(s) (e.g., 8 memory cells per byte). For volatile memorydevices, the memory cells must be periodically “refreshed” in order tomaintain their state. Such memory devices are usually fabricated fromsemiconductor devices that perform these various functions and arecapable of switching and maintaining the two states. The devices areoften fabricated with inorganic solid state technology, such as,crystalline silicon devices. A common semiconductor device employed inmemory devices is the metal oxide semiconductor field effect transistor(MOSFET).

The use of portable computer and electronic devices has greatlyincreased demand for non-volatile memory devices. Digital cameras,digital audio players, personal digital assistants, and the likegenerally seek to employ large capacity non-volatile memory devices(e.g., flash memory, smart media, compact flash, . . . ).

Because of the increasing demand for information storage, memory devicedevelopers and manufacturers are constantly attempting to increasestorage capacity for memory devices (e.g., increase storage per die orchip). A postage-stamp-sized piece of silicon may contain tens ofmillions of transistors, each transistor as small as a few hundrednanometers. However, silicon-based devices are approaching theirfundamental physical size limits. Inorganic solid state devices aregenerally encumbered with a complex architecture which leads to highcost and a loss of data storage density. The volatile semiconductormemories based on inorganic semiconductor material must constantly besupplied with electric current with a resulting heating and highelectric power consumption in order to maintain stored information.Non-volatile semiconductor devices have a reduced data rate andrelatively high power consumption and large degree of complexity.

Currently, devices that can store large amounts of data in a nonvolatilemanner, such as hard drives and optical media, are also physicallylarge. These devices require a means to rotate the media so informationcan be stored and read. This requires additional power, parts and sizenot required by solid state type memory devices. Thus, when size is afactor, solid state memory is normally utilized. Tremendous strides havebeen accomplished in decreasing the size of these types of memory. A onesquare centimeter sized piece of silicon may contain tens of millions ofsolid state entities. Despite the great improvements in the solid statearea, society continues to demand better and smaller memory devices.

Inorganic type solid state semiconductor devices generally requireintricate architectures that directly drive production costs up and datastorage density down. The nonvolatile variety of these semiconductordevices consumes a relatively high amount of power to change states.And, the volatile variety of these semiconductor devices requires aconstant voltage source that consumes even more power than thenonvolatile type.

SUMMARY OF THE INVENTION

The following is a summary of the invention in order to provide a basicunderstanding of some aspects of the invention. This summary is notintended to identify key/critical elements of the invention or todelineate the scope of the invention. Its sole purpose is to presentsome concepts of the invention in a simplified form as a prelude to themore detailed description that is presented later.

The present invention provides semiconductor devices that possess one ormore of the following: small size compared to inorganic semiconductordevices, capability to store information short term and/or long term,quick operational response time, lower operating voltages, low cost,high reliability, long life, increased current flow over inorganicsemiconductor devices, low temperature processing, light weight, andhigh density.

One aspect of the present invention relates to an organic memory devicewith selectively conductive decay media. This allows variability of thedensity and variability of the persistence of stored data by altering aresistive state of the organic memory device. Thus, a single device canbe utilized, at will, as a long term information storage device with asmaller variable density range and/or as a short term informationstorage device with a larger variable density range. The same device canbe operated in a mixed mode that can be comprised of a plurality ofcells having long term storage capability with a small density range; aplurality of cells having a medium term storage capability with a mediumdensity range; and/or a plurality of cells having short, medium, andlarge density ranges. This eliminates the need for multiple types ofstorage devices (e.g., volatile and nonvolatile), simplifying memorycircuitry, and increasing information storage persistence flexibility ona cell by cell basis.

In another aspect in accordance with the present invention, a graphicaltechnique varies an amount of memory density versus a retention time ofa resulting memory cell. It is to be appreciated varying a memorydensity versus retention time is a natural extension of a measuredresponse of a utilized memory material. In one aspect in accordance withthe present invention, a voltage is applied to a memory cell providingvarying densities, wherein the varying density provides an increase ordecrease in retention time. Based at least in part upon a measuredresponse curve for a memory material, resistive states are available toa memory cell, wherein an applied voltage changes resistance. Theresistance change allows a memory cell to operate in a resistive state,wherein the resistive state is associated with a retention time. Amemory cell having more resistive states correlates to a limitedretention time. Conversely, a memory cell having limited resistivestates correlates to a substantial retention time.

Another aspect of the present invention relates to a method offabricating an organic semiconductor device utilizing selectivelyconductive decay media. This allows formation of an organic memorydevice that can alter its density and persistence of stored informationbased upon a resistive state. Fabricating the organic semiconductordevice according to the present invention, produces a highly flexibledevice that can replace multiple devices while decreasing power and arearequirements, thus, reducing manufacturing costs and increasing devicedensity.

Yet another aspect of the present invention relates to a system with ameans to determine a level of persistence for information to be storedinto memory and a means for setting a resistive state of an organicmemory cell based on the level of persistence.

Still yet another aspect of the present invention relates to a systemfor controlling an organic memory device with a means for determining apower state of a device utilizing an organic memory cell comprising aselectively conductive decay media and a means for setting at least oneresistive state of at least one organic memory cell based, at least inpart, upon a current power state and/or an imminent power state (e.g.,ON, OFF, standby, hibernation, and the like).

To the accomplishment of the foregoing and related ends, the inventioncomprises the features hereinafter fully described and particularlypointed out in the claims. The following description and the annexeddrawings set forth in detail certain illustrative aspects andimplementations of the invention. These are indicative, however, of buta few of the various ways in which the principles of the invention maybe employed. Other objects, advantages and novel features of theinvention will become apparent from the following detailed descriptionof the invention when considered in conjunction with the drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a three dimensional diagram of an organic memory device inaccordance with an aspect of the present invention.

FIG. 2 is a graphical technique that can be employed in an organicmemory device in accordance with an aspect of the present invention.

FIG. 3 is a three dimensional diagram of a passive layer that can beemployed in an organic memory device in accordance with an aspect of thepresent invention.

FIG. 4 is a three dimensional exploded view diagram illustrating anorganic conductor layer formed by a CVD process in accordance with anaspect of the present invention.

FIG. 5 is a three dimensional diagram illustrating another organicconductor layer formed by a CVD process in accordance with an aspect ofthe present invention.

FIG. 6 is a three dimensional diagram of yet another organic conductorlayer formed by a CVD process in accordance with an aspect of thepresent invention.

FIG. 7 is a graph depicting the effect of an intrinsic electric field onan interface between a passive layer and an organic conductor layer inaccordance with an aspect of the present invention.

FIG. 8 is a graph illustrating charge carrier concentration of anexemplary memory device in accordance with an aspect of the presentinvention.

FIG. 9 is a graph illustrating charge carrier concentration of anexemplary memory device in accordance with an aspect of the presentinvention.

FIG. 10 is a graph illustrating charge carrier concentration of anexemplary memory device in accordance with an aspect of the presentinvention.

FIG. 11 is a graph illustrating charge carrier concentration of anexemplary memory device in accordance with an aspect of the presentinvention.

FIG. 12 is a graph illustrating charge carrier concentration at theinterface of an exemplary memory device as function of applied voltagein accordance with an aspect of the present invention.

FIG. 13 is a graph illustrating charge carrier concentration at theinterface of an exemplary memory device as function of applied voltagein accordance with an aspect of the present invention.

FIG. 14 is a block diagram depicting an organic memory device in variousstates in accordance with an aspect of the present invention.

FIG. 15 is a three dimensional view of an organic memory device inaccordance with an aspect of the present invention.

FIG. 16 is a flow diagram illustrating a method of fabricating anorganic memory device in accordance with an aspect of the presentinvention.

FIG. 17 is another flow diagram illustrating a method of fabricating anorganic memory device in accordance with an aspect of the presentinvention.

DETAILED DESCRIPTION OF THE INVENTION

The following is a detailed description of the present invention made inconjunction with the attached figures, wherein like reference numeralswill refer to like elements throughout.

The present invention is an organic memory device that has thecapability to alter its density and level of persistence by changing aresistive state of the organic memory device. The resistive state ischanged by applying a voltage potential across an organic memory cellcomposed of a selectively conductive decay media. A single cell can beset at different resistances to allow multiple bit states per cell whichprovides a higher device density. At high resistive states, a device'sdensity can be altered in a wide range. For example, at a high resistivestate of approximately 10,000 ohms, a single cell can have variablestates in a substantially similar order of magnitude with asubstantially similar level of persistence. Therefore, the presentinvention provides higher density memory devices and the flexibility tochange in an opposite direction. Thus, a high resistive state providesshort persistence and a low resistive state provides long persistence.This produces a device capable of being a long term and/or a short termmemory storage device. Therefore, the need for separate long term (e.g.,nonvolatile) and short term (e.g., volatile) memory is eliminated.Additionally, a device is provided that operates with a higher densityin a short term state and/or operates with a lower density in a longterm state. A higher resistive state of a device requires less voltage(power) to operate. Thus, a device operates with low power in a shortterm state and/or operates with high power in a long term state. Thepresent invention also drastically reduces the power requirements forboth short and long term storage compared to typical inorganic volatileand nonvolatile memory devices.

The present invention provides this capability via a selectivelyconductive decay media which is controlled by the resistive state of anorganic memory cell. A high and/or low resistive state can provide afast and/or slow rate of conductive decay, increasing a conductiveperiod (retention time). One aspect of the present invention, forexample, can have a high resistive state equating to an exponentialconductivity decay rate. Another aspect of the present invention canhave a low resistive state equating to a logarithmic or even slowerconductivity decay rate. In this manner, the decay rate controls thepersistence of stored information in the organic memory cell. Variouslevels of persistence can be achieved by altering the composition of theselectively conductive decay media. One skilled in the art canappreciate the level of flexibility afforded by the present invention.Resistive states, rates of decay and voltage potentials can all beutilized to facilitate a level of persistence of the stored informationin the organic memory cell.

Varying the density and storage method is advantageous for many reasons.In one instance of the present invention, utilizing a memory device inshort term mode (e.g., similar to DRAM and other volatile memorydevices) can be achieved while a semiconductor device, such as acomputer and the like, is under power. Long term mode (e.g., similar toflash memory and other nonvolatile memory devices) can then be setbefore the device is shutdown, providing long term storage. This allowsfor almost instantaneous restarts after power is once again applied tothe device, eliminating loading volatile memory upon power-up. Inanother instance of the present invention, for example, memory for amobile cellular telephone and the like can be switched from high density(short persistence) during high-speed, large memory device operation tolow density (long persistence) during low-speed, long-term criticalmemory operations, reducing power demands. In yet another instance ofthe present invention, typical high speed memory performance is achievedwith a voltage potential of a range of approximately 3 to 5 volts.Similarly, a state of a memory device can typically be read with avoltage potential from about 10 to about 200 millivolts.

In FIG. 1, a diagram of an organic memory device in accordance with anaspect of the present invention is shown. The memory device includes afirst electrode 104, a passive layer 106, an organic conductor layer 108and a second electrode 110. The diagram also illustrates a voltagesource 102 connected to the first electrode 104 and the second electrode110 that applies a voltage on the first electrode 104 and the secondelectrode 110.

The first electrode 104 and the second electrode 110 are comprised of aconductive material. The thickness of the first electrode 104 and thesecond electrode 110 can vary depending on the implementation and thememory device being constructed. The organic conductor layer 108 and thepassive layer 106 are collectively referred to as a selectivelyconductive decay media. The conductive decay properties of this media(e.g., exponential decay rate, logarithmic decay rate, and the like) canbe modified in a controlled manner by applying varying voltagepotentials across the media via the electrodes 104 and 110 in order toalter a resistive state of the organic memory device.

The organic conductor layer 108 is comprised of a conjugated organicmaterial. If the organic layer is a polymer, a polymer backbone of theconjugated organic polymer may extend lengthwise between the electrodes104 and 110 (e.g., generally substantially perpendicular to the inner,facing surfaces of the electrodes 104 and 110). The conjugated organicmolecule can be linear or branched such that the backbone retains itsconjugated nature. Such conjugated molecules are characterized in thatthey have overlapping π orbitals and that they can assume two or moreresonant structures. The conjugated nature of the conjugated organicmaterials contributes to the conductive decay properties of theselectively conductive decay media.

In this configuration, the conjugated organic material has the abilityto donate and accept charges (holes and/or electrons). Generally, theconjugated organic molecule has at least two relatively stableoxidation-reduction states. The two relatively stable states permit theconjugated organic polymer to donate and accept charges and electricallyinteract with the passive layer. The organic materials may be cyclic oracyclic. Additionally, the conjugated polymer can be doped and dedopedby dopant such as with metal ions or neutral materials.

For some cases such as organic polymers, the organic material selfassembles between the electrodes during formation or deposition. Theorganic conductor layer 108 has a suitable thickness that depends uponthe chosen implementations and/or the memory device being fabricated.This layer 108 can be formed by a number of suitable techniques. Onesuch technique is spin-on which involves depositing a mixture of thematerial and a solvent, and then removing the solvent from thesubstrate/electrode. Another suitable technique is chemical vapordeposition. CVD includes low pressure chemical vapor deposition (LPCVD),plasma enhanced chemical vapor deposition (PECVD), and high densitychemical vapor deposition (HDCVD). It is not typically necessary tofunctionalize one or more ends of the organic molecule in order toattach it to an electrode/passive layer. Sometimes, it may have achemical bond formed between the conjugated organic polymer and thepassive layer 106.

The passive layer 106 contains at least one charge carrier assistingmaterial that contributes to the controllable conductive decayproperties of the selectively conductive decay media. The charge carrierassisting material has the ability to donate and accept charges (holesand/or electrons). Generally, this material has at least two relativelystable oxidation-reduction states. These states permit the chargecarrier assisting material to donate and accept charges and electricallyinteract with the organic conductor layer 108. The particular chargecarrier assisting material employed is selected so that the tworelatively stable oxidation states match with the two relatively stableoxidation states of the conjugated organic molecule of the layer 108.

The passive layer 106 can in some instances act as a catalyst whenforming the organic conductor layer 108. In this configuration, thebackbone of the conjugated organic molecule may initially form adjacentthe passive layer 106, and grow or assemble away and substantiallyperpendicular to the passive layer surface. As a result, the backbonesof the conjugated organic molecules may be self aligned in a directionthat traverses the two electrodes.

Examples of charge carrier assisting materials that may make up thepassive layer 106 include one or more of nickel arsenide (NiAs), cobaltarsenide (CoAs₂), copper sulfide (Cu₂S, CuS), copper oxide (CuO, Cu₂O),manganese oxide (MnO₂), titanium dioxide (TiO₂), indium oxide (I₃O₄),silver sulfide (Ag₂S, AgS), iron oxide (Fe₃O₄), and the like. Thepassive layer 106 may be grown using oxidation techniques, formed by gasphase reactions, or deposited between the electrodes. The passive layer106 has a suitable thickness that can vary on the implementation and/ormemory device being fabricated.

In order to facilitate operation of the organic memory device, theorganic conductor layer 108 is generally thicker than the passive layer106. In one aspect, the thickness of the organic conductor layer is fromabout 1 to about 500 times greater than the thickness of the passivelayer. It is appreciated that other suitable ratios can be employed inaccordance with the present invention.

The organic memory device, like conventional memory devices, can havetwo states, a low impedance or “ON” state or high impedance or “OFF”state. However, unlike conventional memory devices, the organic memorydevice is able to maintain a plurality of states, in contrast to aconventional memory device that is limited to two states (e.g., OFF orON). The organic memory device can employ varying degrees of resistivityto identify additional states. For example, the organic memory devicecan have a very low impedance state, a low impedance state, a mediumlevel impedance state, and a high impedance state. This enables thestorage of multiple bits of information in a single organic memorydevice, such as 2 or more bits of information or 4 or more bits ofinformation (e.g., 4 states providing 2 bits of information, 8 statesproviding 3 bits of information, etc.). It also allows certain impedancestates, for example, such as an extreme high and/or low resistive stateto be utilized to trigger different conductive decay rates within theselectively conductive decay media. Thus, an organic memory cellutilizing the present invention can both store different states forinformation storage and, at the same time, allow the conductivity decayrate to be altered, providing long and/or short term information storageas required. This can be accomplished on a cell by cell basis as opposedto conventional memory devices that are either all short term or alllong term memory cells.

During typical device operation, electrons flow from the secondelectrode 110 through the selectively conductive decay media to thefirst electrode based on a voltage applied to the electrodes by thevoltage source 102 if the organic conductor layer 108 is an n-typeconductor. Holes flow from the first electrode 104 to the secondelectrode 110 if the organic conductor layer 108 is a p-type conductor.Both electrons and holes flow in the organic conductor layer 108 if itcan be both n- and p-type with the proper energy band match with thepassive layer 106 and second electrode 110. As such, current flows fromthe first electrode 104 to the second electrode 110 through theselectively conductive decay media.

Switching the organic memory device to a particular state is referred toas programming or writing. Programming is accomplished by applying aparticular voltage above a threshold voltage such as, for example, 9volts, 2 volts, and/or 1 volt and the like (assuming these voltagelevels are above a given threshold voltage), across the selectivelyconductive decay media by the electrodes 104 and 110. A device operationmode can be set by this particular operation voltage. Thus, there istypically a separate threshold voltage that corresponds to a respectivedesired state (e.g., “OFF”; “ON”). The threshold value varies dependingupon a number of factors including the identity of the materials thatconstitute the organic memory device, the thickness of the variouslayers, and the like. The voltage supply 102 is controllable andemployed to apply the threshold voltage in this aspect of the invention.However, other aspects of the invention can utilize other means to applythreshold voltages.

Generally speaking, the presence of an external stimuli such as anapplied electric field that exceeds a threshold value (“ON” state)permits an applied voltage to write from the organic memory device;whereas the absence of the external stimuli that exceeds a thresholdvalue (“OFF” state) prevents an applied voltage to write or eraseinformation into/from the organic memory device.

To read information from the organic memory device, a voltage orelectric field (e.g., 0.2 volts, 0.1 volts, 0.05 volts, etc.) is appliedby the voltage source 102. Then, an impedance measurement is performedthat determines the operating state of the memory device (e.g., highimpedance, very low impedance, low impedance, medium impedance, and thelike). As stated previously, the impedance relates to, for example, “ON”(e.g., 1) or “OFF” (e.g., 0) for a dual state device. Multiple bitstates per cell are achieved by applying different voltage levels abovea threshold voltage. For example, a cell can be set at resistance R1,R2, R3, and R4 at four different voltages (e.g., 2.0, 1.98, 1.96, and1.97) corresponding to “00”, “01”, “10”, or “11” for a quad statedevice. It is appreciated that other numbers of states can provide otherbinary interpretations. A device can be operated in a long term modethat is usually also a low density mode, and usually a low speed mode(or high speed mode using much higher voltages). In an opposingoperation mode (short term, high density), a device can be operatedusing low voltages. To erase information written into the organic memorydevice, a negative voltage or a polarity opposite the polarity of thewriting signal that exceeds a threshold value is applied. Additionally,altering resistive (impedance) states at the extreme spectrums can beone aspect of utilizing the present invention to alter the conductivedecay rate to produce long term and/or short term storage.

Now turning to FIG. 2, a graphical representation 200 of varying anamount of memory density in accordance with the present invention isillustrated. The present invention utilizes a novel concept of varyingan amount of memory density versus a retention time of a resultingmemory cell, wherein a voltage applied to the memory cell provides achange in resistance. Changing resistance in a memory cell allowsdiffering densities to exist, which in turn, varies the retention timeof such memory cell. FIG. 2 illustrates a measured response curve 202for a memory material, wherein such measured response curve 202 isplotted as a function of initial programmed resistance for each cell(in, for example, Ohms) and retention time. Based at least in part uponmeasured response curve 202 for a memory material, numerous resistivestates (collectively referred to as resistive states 204) of a memorycell are available. Such resistive states are illustrated as 204 ₁, 204₂, 204 ₃, 204 ₄, 204 ₅, 204 ₆, 204 ₇, and 204 ₈. It is to be appreciateda memory cell can be established in a resistive state and more availableresistive states imply higher densities. For example, a voltage can beapplied to a first memory cell changing a resistance to 100K. Such firstmemory cell can utilize 8 resistive states based upon a density level(e.g., a density level provided by the resistance change created by anapplied voltage). Continuing with the example, a second memory cell canbe created such that the voltage applied changes a resistance level to1K, wherein such resistance level provides 2 resistive states.Furthermore, the first memory cell and the second memory cell will havedifferent retention times based at least in part upon the resistivestate. It is to be appreciated the novel concept of varying an amount ofmemory density versus a retention time of a resulting memory cell can beassociated with one memory cell and/or a plurality of memory cells.

For example, FIG. 2 is a graphical representation 200 in accordance withone aspect of the present invention utilizing a measure response curve202 for a memory material, wherein such memory response curve 202 for amemory material provides capabilities of two co-existing operatingregions. A first region A is depicted such that a memory cell has alimited retention time 206. Region A provides a wide choice of resistivestates 204, yet data retention time is determined by a highest resistivestate. Thus, region A provides 8 resistive states 204, but only alimited retention time 206. It is to be appreciated that numerousresistive states imply high density. A second region B is illustrated,wherein a memory cell has a substantial retention time 208. Region Bprovides limited resistive states (specifically 204 ₇ and 204 ₈), but asubstantial retention time 208. Thus, region B provides only 2 resistivestates, but a substantial retention time 208. Additionally, it is to beappreciated limited resistive states imply low density.

Referring to FIG. 3, a three dimensional diagram that depictsfabrication of a passive layer 300 in accordance with an aspect of thepresent invention is depicted. A charge carrier assisting material layeris formed by a gas phase reaction operation. A first layer 306 is formedthat comprises an element such as Cu. A second layer 304 is formed onthe first layer. The second layer comprises charge carrier assistingmaterial such as Cu_(y)S (e.g., Cu₂S, CuS or mixture of both). A thirdlayer 302 is formed on the second layer 304. The third layer 302contains elements/compounds such as Cu₂O, and/or CuO. It is appreciatedthat alternate aspects of the invention can employ suitable variationsin composition and thickness and still be in accordance with the presentinvention. Thus, the passive layer 300, in one instance of the presentinvention, can be multiple layers of passive materials and/or passivelayers.

Looking at FIG. 4, a three dimensional exploded view diagramillustrating an organic conductor layer 400 formed by a chemical vapordeposition (CVD) process in accordance with an aspect of the presentinvention. The layer 400 is formed by a gas phase reaction process.Typically, the organic conductor layer 400 is formed in contact with apassive layer 402 and an electrode 404. The organic conductor layer 400is comprised of polydiphenylacetylene (DPA).

Turning now to FIG. 5, a three dimensional diagram depicting anotherorganic conductor layer 500 formed from a CVD process in accordance withan aspect of the present invention is illustrated. Once again, theorganic conductor layer 502 is formed by a gas phase reaction processand is very thin compared to the passive layer. The organic conductorlayer 502 is formed in contact with a passive layer 504 and an electrode506. The organic conductor layer 502 is comprised of polyphenylacetylene(PPA).

In FIG. 6, a three dimensional diagram of another organic conductorlayer 602 formed by spin coating in accordance with an aspect of thepresent invention is illustrated. The organic conductor layer 602 isformed by a spin coating process, instead of a gas phase reactionprocess. The organic conductor layer 602 is formed in contact with apassive layer 604 and an electrode 606. The organic conductor layer 602is comprised substantially of PPA and has a thickness of about 100 Å.

Experimental results tend to show organic layers formed by spin coatingyield a more reliable polymer layer than polymer layers formed by CVD.This may be due to the presence of oxygen and lack of control of heatgenerated by polymerization under CVD. It is appreciated thatcontrolling heat and oxygen during polymerization for CVD processes canimprove the resulting polymer layer. Additionally, organic layerscreated by CVD can be very thin compared to those created with othermethods.

It is to be appreciated that various alternatives to and variations ofthe layers described in FIGS. 3-6 can be employed in accordance with thepresent invention.

The passive layer (e.g., CuS) employed in organic memory devices play animportant role. Its presence significantly decreases the resistivity(impedance) of the organic layer, and changes the persistence state of adevice. There are at least two mechanisms that are believed to allow thepassive layer to play this role. One (or two) of the mechanisms maydominate in a device depending on the material of the passive layer.

A first mechanism is believed to be an electronic process that involvescharge carriers, such as holes and electrons, during an operation of adevice. The passive layer has at least a function in the following:charge carrier generation by the charge carrier assisting material,charge carrier distribution in organic material, and memory loss due tocharge carrier redistribution after reversing an electric field. Thediscussion below describes and illustrates charge carrier concentrationand models behavior of organic memory devices.

The following discussion uses conductive polymer as the organic materialand CuS as an example of a charge carrier assisting material utilized inthe present invention. However, the discussion can also be appliedgenerally to other like charge carrier assisting materials. With respectto charge carrier generation, the copper in CuS is at its highestoxidation state Cu(II). It has relatively strong capability to gainelectrons from a contacting polymer and yields the following equation:Cu(II)S+Polymer→Cu(I)S⁻+Polymer⁺  (1)The consequence is that an intrinsic field is produced due to thecharges accumulated on the interface between CuS and polymer. This isillustrated in FIG. 7, which is a three dimensional graph depicting theeffect of an intrinsic electric field on an interface between a passivelayer and a polymer. The oxidized polymer (Polymer⁺) is the chargecarrier when external field is applied. The conductivity (or1/resistivity) of polymer is determined by its concentration and itsmobility by:σ=qpμ  (2)where q is the charge of the carrier, p is carrier concentration, and μis the mobility.

Referring now to the charge depletion layer, employing a similar conceptas applied with respect to semiconductors, a potential function can beexpressed as:V(x)=qN _(p)(d _(p) x−x ²/2)/∈  (3)where N_(p) is the average concentration of charge carrier, ∈ is thedielectric constant of the polymer, and d_(p) is the width of the chargedepletion. N_(p) can be obtained by employing the following equation:

$\begin{matrix}{d_{p} = \left\lbrack \frac{2{ɛ\left( {V_{b} \pm V} \right)}}{{qN}_{p}} \right\rbrack^{1/2}} & (4)\end{matrix}$where V is the external field voltage applied. For forward voltage, itis “−” sign. For the reverse voltage, it is “+” sign. The voltagefunction of Eq. (3) can be approximated to simplify the derivation.

With respect to charge carrier distribution, like p-doping of asemiconductor, two processes typically take place in the electric field.This flux can be expressed as:

$\begin{matrix}{J = {{{- {qD}}\frac{\mathbb{d}p}{\mathbb{d}x}} + {q\mu pE}}} & (5)\end{matrix}$where D is the diffusion constant of the charge carrier, and E is theelectric field at x.

When the forward voltage is so large that the current flux J>0, theanalytical equation can be derived for steady state flow with someassumption for the voltage distribution in the device. Overall, underforward voltage, the charge distribution p(x) is an increase function ofx. When reverse voltage is applied, V(x)>V₀, the charge concentration isa decrease function of x.

The final characteristic, conductivity period (retention time), refersto the fact that a forward voltage produces more charge carrier and thecharge carrier accumulates more on the other end of the passive layer(away from the organic material). However, this charge carrierconcentration will be set back once the voltage is removed, whichincludes two processes: charge carrier diffusion toward the passivelayer and charge carrier recombination on the interface.

Fick's Law can describe the 1st process, charge carrier diffusion towardthe passive layer.

$\begin{matrix}{\frac{\mathbb{d}p}{\mathbb{d}t} = {D\frac{\mathbb{d}^{2}p}{\mathbb{d}^{2}x}}} & (6)\end{matrix}$The charge carrier recombination can be described as follows:Cu(I)S⁻+Polymer⁺→Cu(II)S+Polymer  (7)This conductivity decay rate (reaction rate) is expressed as:

$\begin{matrix}{\frac{\mathbb{d}{p(0)}}{\mathbb{d}t} = {k_{0}{p(0)}{n(0)}}} & (8)\end{matrix}$where k₀ is conductivity decay rate constant and it is temperaturedependent.

The conductivity period is the time required to redistribute the chargecarrier to the original state and can be determined by equations 6 and8. It is believed that a higher injected charge carrier concentrationexists in a polymer layer because of a forward external field, and,thus, a longer time is required to allow a system to recover to aninitial state. That means the persistence of a device is determined bythe injected charge carrier under the influence of the external field.Therefore, variable persistence can be achieved by adjusting an externalvoltage that provides the external field. It is likely that theconductivity decay rate depicted in Eq. 8 is relatively faster thandiffusion rate. Therefore, the conductivity period can be substantiallydetermined by the diffusion process only. Thus, choosing materials thathave diffusion rates that can be varied via voltage potentials, allowsthe present invention to dynamically alter a storage period of anorganic memory cell.

An exemplary memory device is considered herein with respect to theequations 1-8 discussed above and illustrated in FIGS. 8-13.

FIG. 8 depicts a graph 800 of charge carrier concentration 801 of theexemplary memory device as a function of distance from the passive layerand the organic material interface in accordance with an aspect of theinvention. The charge carrier concentration 801 is shown as being adecreasing function of distance (x) from the interface. This graph 800assumes an external voltage V=0 and a current J=0. The charge carrierconcentration 801 is derived utilizing Eq. 5 with a constant fieldassumption. However, the graph shown is independent of the constantfield assumption.

Turning now to FIG. 9, another graph 900 illustrating charge carrierconcentration 901 for the exemplary organic memory device is depicted inaccordance with an aspect of the present invention. For this graph 900,parameters are set as follows: forward voltage >0V and current flux J=0.The passive layer has a higher voltage than the organic conductor layer.This drives the charge carrier away from the passive layer and leads tocharge carrier concentration that has an increase function of distance(x). Even at lowest concentration, p(0) is not a small value. Thisexplains why the organic material is a good conductor (low resistivity)when forward voltage is applied. Again, it is Eq. 6 with constantelectric field model used for the plot. The points demonstrated areindependent of constant electric field assumption.

FIG. 10 depicts yet another graph 1000 of charge carrier concentration1001 of the exemplary memory device as a function of distance from thepassive layer and the organic material interface in accordance with anaspect of the invention. For this graph, the parameters are set suchthat the reverse voltage >0V and the current J=0. With reversed voltage,the charge carrier is concentrated at the passive layer and the organicmaterial interface. It drops quickly to a small concentration when it isaway from the interface, causing high resistivity when a high reversedvoltage applied. Again, Eq. 5 with constant electric field model isassumed for the graph.

Referring now to FIG. 11, another graph 1100 that depicts charge carrierconcentration 1101 of the exemplary memory device as a function ofdistance in accordance with an aspect of the present invention isprovided. For this graph 1100, parameters are set as follows: forwardvoltage >0V and current flux J>0. When current flux J>0, the chargecarrier is still an increase function of x because the forward voltagedrives the charge carrier away from the passive layer interface. Oneimportant point is that the lowest concentration p(x) is at interface.

Moving on to FIG. 12, yet another graph 1200 of charge carrierconcentration at the interface 1201 of the exemplary memory device as afunction of forward voltage is depicted. For this graph, the parametersare set such that J initially=0 at low voltage and starts to be >0 whenvoltage reaches a threshold, and assumes a constant electric fieldmodel. The interface charge carrier concentration initially decreasesand reaches minimum at a threshold voltage and starts to increase asvoltage increases. This model is applicable when the diffusion constantof the organic material is small and there is constant electricalresistance. With this model, the charge carrier concentration at theinterface is derived as a function of voltage. It is noted that p₀(V)tends to be constant after forward voltage is large enough and thecurrent is controlled by the charge carrier not charge injection at theinterface. As such, p(0) can be rewritten as:

$\begin{matrix}{{p(0)} = {\frac{1}{2}\left\{ {{- {K_{eq}\lbrack{Polymer}\rbrack}_{0}} + \sqrt{\left( {K_{eq}\lbrack{Polymer}\rbrack}_{0} \right)^{2} + \frac{4{\mathbb{d}_{CuS}{{K_{eq}\lbrack{Polymer}\rbrack}_{0}\lbrack{CuS}\rbrack}_{0}}}{\mathbb{d}}}} \right\}}} & (9)\end{matrix}$This Eq. 9 shows that limiting p(0) is an increase function of thicknessratio between the passive layer and the polymer layer.

Referring to FIG. 13, another graph 1300 that depicts charge carrierconcentration at the interface 1301 as a function of forward voltage isshown. For this graph 1300, p(0) is a function of forward voltage,current J, which may or may not be =0, and a step potential functionmodel. This model assumes the voltage V(x) function can be described bya step function. The model is applicable when the diffusion constant ofthe polymer is very large. Therefore, the electrical resistance(resistive state) in the device is minimal. With this model, the chargecarrier concentration at the interface is derived as the function ofvoltage. It is noted that in FIG. 13 that p₀(V) tends to be zero afterforward voltage is large enough. When the charge carrier at theinterface controls the current flux, this value is a function ofvoltage. This zero limit behavior is due to the interface boundary limitset by the reaction (1). Basically, the fast charge carriertransportation from the interface to the other end reaches the supplylimit. Thus, the limiting p(0) is also rewritten as:

$\begin{matrix}{{p(0)} = {\frac{1}{2}\left\{ {{- {K_{eq}\lbrack{Polymer}\rbrack}_{0}} + \sqrt{\left( {K_{eq}\lbrack{Polymer}\rbrack}_{0} \right)^{2} + \frac{4{\mathbb{d}_{CuS}{{K_{eq}\lbrack{Polymer}\rbrack}_{0}\lbrack{CuS}\rbrack}_{0}}}{\mathbb{d}\left\lbrack {{\exp\frac{{V(0)} - V}{V_{t}}} - \frac{{V(0)} - V}{V_{t}}} \right\rbrack}}} \right\}}} & (10)\end{matrix}$Again p(0) is an increase function of thickness ratio between thepassive layer and the polymer layer.

Regarding the above discussion, it is important to note that the fluxmeasured is determined by charge carrier drift when limiting flux is inthe organic material. Under constant electric field assumption, thefunction to describe the charge carrier concentration is p(x)·p_(j)=p(0)is met when the organic material determines limiting flux since thelowest concentration in the device is at the interface. This conditionresults in a constant p(x). This means the diffusion contribution to theflux in Eq. 5 is zero. Under step potential assumption, another functionis employed to describe the charge carrier concentration p(x). Theinitial charge carrier concentration p(0) has a relatively substantiallysmaller value than other regions. Therefore, J is still determined byp(0). Another point that is noted regards boundary conditions. Unlikesemiconductors, it is only applicable to the concentration at theinterface, not everywhere. This boundary condition limits the totalamount of the charge carrier produced in the device.

The equations above (E.q. 1-8) and FIGS. 9-12 describe and modelbehavior of an aspect of the present invention. This model can beemployed to explain measured data and can be for other passive layermaterials aside from CuS. Additionally, the model can be used todetermine how to improve conductivity periods (retention) and responsetime and to design other devices such as a transistor. Further, themodel can be employed to develop various threshold voltages that set theresistive (impedance) states, read the conductivity levels and erase theconductivity levels, thus performing memory device operations of writingor programming, reading, erasing, and retention time (conductivityperiods).

In FIG. 14, a block diagram that illustrates an organic memory device1400 in various states in accordance with an aspect of the presentinvention is illustrated. The device 1400 is depicted in a first “OFF”state 1401, an “ON” state 1402, and a second “OFF” state 1403. It isappreciated that memory devices formed in accordance with the presentinvention also has long and/or short retention states (not shown) andcan have other states than those depicted in FIG. 14. The organic memorydevice 1400 comprises a top electrode 1404, a bottom electrode 1406 anda selectively conductive decay media layer 1408 comprising an organicconductor layer (e.g., PPA) and at least one passive layer (e.g., CuS).

In the first “OFF” state 1401, a positive charge 1410 collects in theselectively conductive decay media layer 1408 near the bottom electrode1406. In the “ON” state 1402, the positive charge 1410 is uniformlydistributed thereby indicating an “ON” state. In the second “OFF” state1403, the positive charge 1410 collects in the selectively conductivedecay media layer 1408 near the top electrode 1404. Likewise, althoughnot illustrated, the positive charges can be induced to remain at theirpositions for a given time (retention time) by applying an appropriatevoltage potential across the selectively conductive decay media layer1408. This effectively produces long and/or short term storage.

A second mechanism is believed to be a process that has ionictransportation and ionic interaction with a polymer. For chelcogenidematerials such as Cu₂S, Ag₂S, it is very common to have metal ions withhigh mobility because of their crystal defects, such as vacancypresence, and thermodynamically available stable phases under the samestoichiometry.Cu2S→Cu⁺+CuS⁻  (11)

These metal ions such as Cu⁺ can move into the contacting polymer undera strong field. The metal ion functions as a dopant in conjugatedpolymer to produce a charge carrier.Cu⁺+Polymer→[Polymer-Cu]⁺  (12)

The interaction between metal ions can be as strong as a ligand bonddepending on the electronic structure of the metal ions and theconjugated polymer. Also, it is determined by an applied field that canpush the metal ion to overcome an energy barrier in order to have properbonding with the conjugated polymer. A fraction of a paired structurebecomes doped and significantly increases the charge carrierconcentration. Thus, a device's conductivity is enhanced dramatically.

The device loses persistence because the reaction reverts direction andmetal ions move back to the passive layer.[Polymer-Cu]⁺→Cu⁺+Polymer  (13)

The persistence of the device is determined by the strength of the“bond” between the polymer and metal ion. A stronger “bond” provides forlonger persistence. Also, it is determined by the concentration of themetal ions in the polymer. The “bond strength” and metal ionconcentration can be adjusted by varying an external electric field.Therefore, variable persistence can be achieved.

Referring to FIG. 15, a three dimensional view of an organic memorydevice 1500 containing a plurality of organic memory devices inaccordance with an aspect of the invention is shown. The organic memorydevice 1500 contains a plurality of first electrodes 1502, a pluralityof second electrodes 1504, and a plurality of memory device layers 1506.Between the respective first and second electrodes are the selectivelyconductive decay media (not shown). The plurality of first electrodes1502 and the plurality of second electrodes 1504 are shown insubstantially perpendicular orientation, although other orientations arepossible. The three dimensional microelectronic organic memory device iscapable of containing an extremely high number of memory devices therebyimproving device density. Peripheral circuitry and devices are not shownfor brevity.

The organic memory devices are useful in any device requiring memory.For example, the organic memory devices are useful in computers,appliances, industrial equipment, handheld devices, telecommunicationsequipment, medical equipment, research and development equipment,transportation vehicles, radar/satellite devices, and the like. Handhelddevices, and particularly handheld electronic devices, achieveimprovements in portability due to the small size and light weight ofthe organic memory devices. Examples of handheld devices include cellphones and other two way communication devices, personal dataassistants, palm pilots, pagers, notebook computers, remote controls,recorders (video and audio), radios, small televisions and web viewers,cameras, and the like. The present invention can also be utilized in anarray of memory cells, enabling long and/or short term memory in asingle device.

In view of the foregoing structural and functional features describedabove, methodologies in accordance with various aspects of the presentinvention will be better appreciated with reference to FIGS. 16-17.While for purposes of simplicity of explanation, the methodologies ofFIGS. 16-17 are depicted and described as executing serially, it is tobe understood and appreciated that the present invention is not limitedby the illustrated order, as some aspects could, in accordance with thepresent invention, occur in different orders and/or concurrently withother aspects from that depicted and described herein. Moreover, not allillustrated features may be required to implement a methodology inaccordance with an aspect the present invention.

Turning to FIG. 16, a flow diagram of a method 1600 of fabricating anorganic memory device in accordance with an aspect of the invention isillustrated. A first electrode is formed on a substrate at 1602. Thefirst electrode is comprised of a conductive material such as, aluminum,chromium, copper, germanium, gold, magnesium, manganese, indium, iron,nickel, palladium, platinum, silver, titanium, zinc, alloys thereof,indium-tin oxide, polysilicon, doped amorphous silicon, metal silicides,and the like. Exemplary alloys that can be utilized for the conductivematerial include Hastelloy®, Kovar®, Invar, Monel®, Inconel®, brass,stainless steel, magnesium-silver alloy, and various other alloys. Thethickness of the first electrode can vary depending on theimplementation and the memory device being constructed. However, someexemplary thickness ranges include about 0.01 μm or more and about 10 μmor less, about 0.05 μm or more and about 5 μm or less, and/or about 0.1μm or more and about 1 μm or less.

After forming the first electrode, a selectively conductive decay medialayer is formed on the first electrode at 1604. The conductive decayproperties of this media (e.g., exponential decay rate, logarithmicdecay rate, and the like) can be modified in a controlled manner byapplying varying voltage potentials across the media via the electrodesand in order to alter a resistive state of the organic memory device.

A second electrode is then formed over the organic layer at 1606. Thesecond electrode is formed of a conductive material in a manner similarto that of the first electrode. The second electrode can, but is notrequired to, be formed of the same conductive material as the firstelectrode.

Turning to FIG. 17, a flow diagram of a method 1700 of fabricating anorganic memory device in accordance with an aspect of the invention isillustrated. A first electrode is formed on a substrate at 1702. Thefirst electrode is comprised of a conductive material such as, aluminum,chromium, copper, germanium, gold, magnesium, manganese, indium, iron,nickel, palladium, platinum, silver, titanium, zinc, alloys thereof,indium-tin oxide, polysilicon, doped amorphous silicon, metal silicides,and the like. Exemplary alloys that can be utilized for the conductivematerial include Hastelloy®, Kovar®, Invar, Monel®, Inconel®, brass,stainless steel, magnesium-silver alloy, and various other alloys. Thethickness of the first electrode can vary depending on theimplementation and the memory device being constructed. However, someexemplary thickness ranges include about 0.01 μm or more and about 10 μmor less, about 0.05 μm or more and about 5 μm or less, and/or about 0.1μm or more and about 1 μm or less.

After forming the first electrode, a passive layer is deposited on thefirst electrode at 1704. The passive layer contains at least one chargecarrier assisting material that contributes to the conductive propertiesof the selectively conductive decay media. The charge carrier assistingmaterial has the ability to donate and accept charges (holes and/orelectrons). Generally, the charge carrier assisting material has atleast two relatively stable oxidation-reduction states. The tworelatively stable states permit the charge carrier assisting material todonate and accept charges and electrically interact with the organicconductor layer. The particular charge carrier assisting materialemployed is selected so that the two relatively stable states match withthe two relatively stable states of the conjugated organic molecules ofthe organic conductor layer.

The passive layer can, in some instances, act as a catalyst when formingthe organic conductor layer. In this configuration, the backbone of theconjugated organic molecule may initially form adjacent the passivelayer, and grow or assemble away and substantially perpendicular to thepassive layer surface. As a result, the backbones of the conjugatedorganic molecules are self-aligned in a direction that traverses the twoelectrodes.

Examples of charge carrier assisting material that may make up thepassive layer include one or more of the following: nickel arsenide(NiAs), cobalt arsenide (CoAs₂), copper sulfide (Cu₂S, CuS), copperoxide (CuO, Cu₂O), manganese oxide (MnO₂), titanium dioxide (TiO₂),indium oxide (I₃O₄), silver sulfide (Ag₂S, AgS), iron oxide (Fe₃O₄), andthe like. The passive layer 1704 is typically grown using oxidationtechniques, formed by gas phase reactions, or deposited between theelectrodes.

The passive layer has a suitable thickness that can vary according tothe implementation and/or memory device being fabricated. Some examplesof suitable thicknesses for the passive layer are as follows: athickness of about 2 Å or more and about 0.1 μm or less, a thickness ofabout 10 Å or more and about 0.01 μm or less, and a thickness of about50 Å or more and about 0.005 μm or less.

Next, an organic conductor layer is formed on the passive layer. Theorganic conductor layer comprises a conjugated molecule(s). Suchconjugated molecules are characterized in that they have overlapping πorbitals and that they can assume two or more resonant structures. Theorganic molecules may be cyclic or acyclic. During formation ordeposition, the organic molecule self assembles between the electrodes.Examples of conjugated organic materials include one or more ofpolyacetylene (cis or trans); polyphenylacetylene (cis or trans);polydiphenylacetylene; polyaniline; poly (p-phenylene vinylene);polythiophene; polyporphyrins; porphyrinic macrocycles, thiolderivatized polyporphyrins; polymetallocenes such as polyferrocenes,polyphthalocyanines; polyvinylenes; polystiroles; and the like.Additionally, the properties of the polymer can be modified by dopingwith a suitable dopant (e.g., salt).

The organic conductor layer is formed with a suitable thickness thatdepends upon the chosen implementations and/or the memory device beingfabricated. Some suitable exemplary ranges of thickness for the organicconductor layer are about 0.001 μm or more and about 5 μm or less, about0.01 μm or more and about 2.5 μm or less, and about a thickness of about0.05 μm or more and about 1 μm or less.

The organic conductor layer can be formed by a number of suitabletechniques, some of which are described above. One suitable techniquethat can be utilized is a spin-on technique that involves depositing amixture of the polymer/polymer precursor and a solvent, and thenremoving the solvent from the substrate/electrode. Another technique ischemical vapor deposition (CVD) optionally including a gas reaction, gasphase deposition, and the like. CVD includes low pressure chemical vapordeposition (LPCVD), plasma enhanced chemical vapor deposition (PECVD),and high density chemical vapor deposition (HDCVD). It is not typicallynecessary to functionalize one or more ends of the organic molecule inorder to attach it to an electrode/passive layer.

In order to facilitate operation of the organic memory device, theorganic conductor layer is generally substantially thicker than thepassive layer. As one example, the thickness of the organic conductorlayer is from about 1 to about 500 times greater than the thickness ofthe passive layer. It is appreciated that other suitable ratios can beemployed in accordance with the present invention.

The conductive decay properties of this media (e.g., exponential decayrate, logarithmic decay rate, and the like) can be modified in acontrolled manner by applying varying voltage potentials across themedia via the electrodes and in order to alter a resistive state of theorganic memory device.

Finally, a second electrode is formed over the organic layer at 1708.The second electrode is formed of a conductive material in a mannersimilar to that of the first electrode. The second electrode can, but isnot required to, be formed of the same conductive material as the firstelectrode.

One skilled in the art can also appreciate that the supra devices andmethods can also be applied to systems that operate devices utilizingthe present invention. A system can be comprised of a means fordetermining a desired persistence for information to be stored in atleast one memory cell and a means for setting at lease one resistivestate of at least one memory cell based, at least in part, upon desiredpersistence for the information. The determination of a desiredpersistence state can include, but is not limited to, determiningwhether information is useful after a power interrupt and/or is criticalto performance of a device during and/or after a power interrupt. A usercould also specify that the information needs to be nonvolatile (e.g.,“backed up”). The system itself could also make the determination as towhat information is critical. This criticality can change dynamicallyand the present invention can also change dynamically with thecriticality change to a short term and/or long term persistence state.Thus, for example, once the criticality of the information is known, theresistive state (and, thus, the decay rate) of the present invention canbe set to reflect a desired persistence state. This can be accomplishedby taking into account materials employed in a selectively conductivedecay media. The media can comprise several decay rates that can bepredetermined and/or dynamically assessed during operation. Theresistive state can be set, for example, by a voltage potential devicedesigned for this purpose and/or by a voltage potential device designedfor reading, writing and erasing a memory cell.

A system can also be comprised of a means for determining a power stateof a device utilizing an organic memory cell comprising a selectivelyconductive decay media and a means for setting at least one resistivestate of at least one organic memory cell based, at least in part, uponat least one selected from the group consisting of a current power stateand an imminent power state. Due to the dynamic capability of thepresent invention to change persistence of stored information, it can beuniquely employed in a system based upon determination of a power stateof a device. This allows the system to perform almost instantaneousboot-up back to a pre-power down state and/or pre-power interruptedstate. Typically, a system has forewarning as to imminent changes inpower states (i.e., soft shutdown). This allows the system to “getready” to shutdown. At this point, a determination can be made to changepersistence of information stored in a memory cell in order to preserveit after shutdown. In the same manner, a system working on and/or usingcritical information can determine that an unexpected power interruptionwould destroy valuable data. If this determination is made, thepersistence of information stored in memory can be changed to protectthe data in case of an unplanned power interrupt. Again, one skilled inthe art can appreciate the tremendous flexibility the present inventionprovides for preserving data, both in a predetermined fashion and alsoin a dynamic fashion. Thus, the brevity of what is described supra isnot meant to limit the scope of the present invention.

What has been described above is one or more aspects of the presentinvention. It is, of course, not possible to describe every conceivablecombination of components or methodologies for purposes of describingthe present invention, but one of ordinary skill in the art willrecognize that many further combinations and permutations of the presentinvention are possible. Accordingly, the present invention is intendedto embrace all such alterations, modifications and variations that fallwithin the spirit and scope of the appended claims. In addition, while aparticular feature of the invention may have been disclosed with respectto only one of several implementations, such feature may be combinedwith one or more other features of the other implementations as may bedesired and advantageous for any given or particular application.Furthermore, to the extent that the term “includes” is used in eitherthe detailed description or the claims, such term is intended to beinclusive in a manner similar to the term “comprising.”

1. An organic memory device, comprising: a first electrode; aselectively conductive decay media formed on the first electrode,responsive to a resistive state of an organic memory device andfacilitating at least one desired characteristic of a state of theorganic memory device; a second electrode formed on the selectivelyconductive decay media; a means for setting at least one resistive stateof the selectively conductive decay media via the first and secondelectrodes, based, at least in part, upon the desired characteristic forthe state of the organic memory device; and a means for determining atleast one resistive state of the selectively conductive decay media viathe first and second electrodes, the means for determining at least oneresistive state comprising applying at least one voltage potentialacross the first and second electrodes, the voltage potential comprisingfrom about 10 to about 200 millivolts.
 2. The device of claim 1, thedesired characteristic comprising a combination of a plurality ofcharacteristics including high impedance, short persistence, highdensity, low power consumption, and high speed.
 3. The device of claim1, the desired characteristic comprising a combination of a plurality ofcharacteristics including low impedance, long persistence, low density,high power consumption.
 4. The device of claim 1, the desiredcharacteristic comprising at least one selected from the groupconsisting of memory impedance, memory persistence, memory density,memory speed, and memory power utilization.
 5. The device of claim 4,the memory persistence comprising at least one persistence modecontrollable via applying at least one voltage potential across thefirst and second electrodes.
 6. The device of claim 4, the memorydensity comprising at least one memory density mode controllable viaapplying at least one voltage potential across the first and secondelectrodes.
 7. The device of claim 4, the memory power utilizationcomprising at least one memory power utilization mode controllable viaapplying at least one voltage potential across the first and secondelectrodes.
 8. The device of claim 4, the memory speed comprising atleast one memory speed mode controllable via applying at least onevoltage potential across the first and second electrodes.
 9. The deviceof claim 8, the memory speed mode comprising at least one selected fromthe group consisting of a writing speed mode and a erasing speed mode.10. The device of claim 9, the writing speed mode comprising a highspeed writing mode that utilizes a range of approximately 2 to 5 voltsof potential across the first and second electrodes to increaseprogramming performance of at least one memory cell.
 11. The device ofclaim 1, the means for setting at least one resistive state includingapplying a voltage potential across the first and second electrodes. 12.The device of claim 1, the means for setting at least one resistivestate including applying a plurality of voltage potentials across thefirst and second electrodes to achieve a plurality of resistive statesrepresentative of multiple bit states per cell in at least one memorycell.
 13. The device of claim 1, the selectively conductive decay mediahaving at least one attribute selected from the group consisting of asubstantially exponential decay of conductivity occurring when theorganic memory device has a high resistive state and a substantiallylogarithmic decay of conductivity occurring when the organic memorydevice has a low resistive state.
 14. The device of claim 1, theselectively conductive decay media comprising a passive layer formed onthe first electrode and an organic polymer layer formed on the passivelayer.
 15. The device of claim 14, the passive layer comprising at leastone selected from the group consisting of nickel arsenide (NiAs), cobaltarsenide (CoAs₂), copper sulfide (Cu₂S, CuS), copper oxide (CuO, Cu₂O),manganese oxide (MnO₂), titanium dioxide (TiO₂), indium oxide (I₃O₄),silver sulfide (Ag₂S, AgS), and iron oxide (Fe₃O₄).
 16. The device ofclaim 14, the organic layer being selected from the group consisting ofpolyacetylene, polyphenylacetylene, polydiphenylacetylene, polyaniline,poly(p-phenylene vinylene), polythiophene, polyporphyrins, porphyrinicmacrocycles, thiol derivatized polyporphyrins, polymetallocenes,polyferrocenes, polyphthalocyanines, polyvinylenes, and polystiroles.17. The device of claim 14, the organic layer having a thickness ofabout 0.001 μm or more and about 5 μm or less.
 18. An organic memorydevice, comprising: a first electrode; a selectively conductive decaymedia formed on the first electrode, responsive to a resistive state ofthe organic memory device and facilitating at least one desiredcharacteristic of a state of the organic memory device, the selectivelyconductive decay media having at least one attribute selected from thegroup consisting of a substantially exponential decay of conductivityoccurring when the organic memory device has a high resistive state anda substantially logarithmic decay of conductivity occurring when theorganic memory device has a low resistive state; a second electrodeformed on the selectively conductive decay media; a means fordetermining a power state of an electronic device utilizing the organicmemory device; and a means for setting at least one resistive state ofthe organic memory device via the first and second electrodes, based, atleast in part, upon at least one selected from the group consisting of acurrent power state and an imminent power state.
 19. The device of claim18, the means for setting at least one resistive state includingproviding long term storage when the current power state is ON and theimminent power state is OFF.
 20. A method of operating an organic memorydevice, comprising: determining at least one desired characteristic forinformation to be stored in at least one memory cell; and setting atleast one resistive state of at least one memory cell based, at least inpart, upon the desired characteristic for the information, the resistivestate having at least one attribute selected from the group consistingof a substantially exponential decay of conductivity occurring when theorganic memory device has a high resistive state and a substantiallylogarithmic decay of conductivity occurring when the organic memorydevice has a low resistive state.
 21. The method of claim 20, thedesired characteristic comprising at least one selected from the groupconsisting of information state, information persistence, informationdensity, and information speed.
 22. The method of claim 20, furtherincluding: determining an appropriate resistive state necessary toachieve the desired characteristic.
 23. The method of claim 22, theappropriate resistive state comprising at least one selected from thegroup consisting of a high resistive state for short term memorypersistence and a low resistive state for long term memory persistence.24. A method of operating an organic memory device comprising:determining a power state of an electronic device utilizing an organicmemory cell comprising a selectively conductive decay media, theselectively conductive decay media having at least one attributeselected from the group consisting of a substantially exponential decayof conductivity occurring when the organic memory device has a highresistive state and a substantially logarithmic decay of conductivityoccurring when the organic memory device has a low resistive state; andsetting at least one resistive state of at least one organic memory cellbased, at least in part, upon at least one selected from the groupconsisting of a current power state and an imminent power state.
 25. Themethod of claim 24, further including altering the resistive state basedupon the power state to provide long term storage when the current powerstate is ON and the imminent power state is OFF.
 26. The device of claim18, the desired characteristic comprising a combination of a pluralityof characteristics including high impedance, short persistence, highdensity, low power consumption, and high speed.
 27. The device of claim18, the desired characteristic comprising a combination of a pluralityof characteristics including low impedance, long persistence, lowdensity, high power consumption.
 28. The device of claim 18, the desiredcharacteristic comprising at least one selected from the groupconsisting of memory impedance, memory persistence, memory density,memory speed, and memory power utilization.